Oil or gas wells are conventionally drilled with a drill string at which point the open hole is not lined, hereinafter referred to as a “borehole”. After drilling, the oil, water or gas well is typically completed thereafter with a casing or liner and a production tubing, all of which from here on are referred to as a “liner”.
Conventionally, during the drilling, production or workover phase of an oil, water or gas well, and from a first aspect of the present invention, there may be a requirement to provide a patch or temporary casing across an interval, such as a damaged section of liner, or an open hole section of the borehole.
Additionally, and from a second aspect of the present invention, there may be a requirement to cut a tubular (such as a section of casing) downhole, remove the upper free part and replace it with a new upper length of tubular in an operation know as a “tie back” and in such a situation it is important to obtain a solid metal to metal seal between the lower “old” tubular section and upper “new” tubular section.
Additionally, from a third aspect, the present invention relates to a seal packer for subterranean wells which can be used to isolate two zones in an annular space of such wells, or to join two tubes together, etc.
The use of radially expandable packers is well known in the art. These packers, or seals, are frequently used to do maintenance in areas over the packer, or to seal off a particular formation, for example a water producing zone of the well.
Generally, there are two types of packers, the first type is inflatable rubber packers and the second type is compact rubber packers. The two types have different characteristics when it comes to the expansion ability and temperature and pressure tolerance. Today, even more well environments have high temperature and pressure, and it is a challenge to develop reliable equipment for such environments. The prior art have some disadvantages, for example the high temperature and high pressure can cause extruding of the packer. Consequently, this may result in a leakage. Another disadvantage is that some packers after compression in well bores with extreme temperatures and pressures will not function properly, for example the relaxation of the packer can work poorly.
There have been several attempts to solve the disadvantages mentioned above.
GB Patent Publication No 2296520A describes oil/gas well tools related to a sealing/packing tool which provides a pressure/fluid barrier. It provides a downhole tool comprising at least one ring with petaloid extensions, said ring being disposed about a longitudinal axis of the tool, and means for controllably deforming said petaloid extensions such that said extensions may be controllably moved in use. Said controllable movement may cause the extensions to be brought into close proximity with an inner surface of a conduit. Said tool may further comprise an elastically deformable packing element. The extensions are expanded by a wedge surface on the ring and help to centre the tool in the conduit. The extensions may also be arranged to act as anti extrusion means for the packing element.
U.S. Patent Publication No 5226492 describes a packer for sealing an annular space comprising a deformable hollow metallic sleeve having an inner cavity which has an open end. The sleeve is preferably cone shaped. An expandable member is disposed within the inner cavity. A wedge member is located in close proximity to the expandable member, and serves to transmit a compressive force to the expandable member to obtain the desired radial expansion of the sleeve. The compression causes the expandable member to be forced around the outside of the wedge member and forms a first seal between the expandable member and an annular production casing. The rim of the metallic sleeve is also in contact with the production casing and accordingly a second seal is formed. Further, the metallic sleeve may comprise one or more slots at desired intervals to facilitate the deformation of the metallic sleeve. Additionally, a seal obtained using an additional band provides improved sealing due to an additional seal formed between the additional band and the inner wall of the production casing.
The main object of the third aspect of the invention is to provide a device which avoids the disadvantages of the prior art. The device according to the invention should be able to seal an annular tube, and also to join two tubes together, in a so-called swage process. Consequently, this requires considerable forces to be applied, which again demand packers with special properties.